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Data Structures, Algorithms, & Applications in C++<BR>

Chapter 12, Exercise 3<BR>

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If there are an odd number of vertices whose degree is odd then

the sum of the degrees of all vertices in the graph is also odd.

However, from Property 2 we know that the sum of the degrees

is <em class=var>2e</em>, which is even.  Therefore, the number

of vertices with odd degree must be even.



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